Wind Powered Battery Charger Engineering Essay

Renewable energy is a burning issue nowadays; different energy resources are being analyzed, tested and improved in order to replace non renewable energy resources. Wind is one of the renewable energy resources which is available in abundance, especially in Europe, huge amount of energy can be produced by using windmills and then this energy can be saved for later usage.

This project looks at the brief history of windmills; their past usage, present usage and future. In addition to this, a prototype circuit is also build which utilizes wind energy to charge 4.5v battery when wind energy is less and 12v battery is charged when high energy is produced by the wind. In addition to this, future recommendations are also made to improve the circuit design.

Acknowledgments

First and foremost, I would like to express my sincere gratitude and appreciation to my supervisors, Mr. Nader Anani. He has been giving me his professional advice and guidance throughout the duration of this work. It was his support and confidence in me that led me to successfully complete this project. It has been a pleasure working under his supervision.

I wish to dedicate this thesis to my family who I dearly love and respect.

Table of Contents

Introduction

In the near future renewable energy resources like solar and wind energy will be replacing conventional non renewable energy resources. Non renewable energy resources are limited in their availability and are running out quickly due to their vast use in the modern society. [1] We rely on coal, oil and gas for running our industries; now that these resources are becoming scarce it is our responsibility to look for other forms of energy so that the future generations do not suffer due to this shortage. A lot of research is being carried out to select a reliable energy resource that can meet the energy demands of the future, which is reliable and efficient.

Energy plays important role in various forms to let human being accomplish different tasks and makes human life easier and more comfortable, from the basic electrical energy that drives electrical and electronic machines and Internet to the kinetic and mechanical energy of vehicles, planes, and all other speedy sources of locomotion. The modern technological world has its own merits and demerits and challenges and issues which are accompanied with it as a result of scientific and industrial revolution and technological advancement. However with exponentially increasing use of devices and equipments requiring power and energy, these sources of energy saw the dreadful event of shortage and rareness. Hence scientists and researchers throughout the world started working on these burning issues and this gave birth to the field of renewable energy.

This project is an attempt to develop a system which utilizes wind energy to efficiently charge up batteries that can be later used as a form of energy.

Aim

The aim of this project is to design, construct and test a battery charger fed from a wind energy source.

Objectives

Objectives of the current project are given below:

Literature review and investigation of wind energy and its history

Proposal of hardware design to build a wind powered battery charger

Development of prototype circuit for charging batteries using Wind Energy

Testing and analysis of the developed system

Discussion on the results obtained

Recommendations for the future work

System Block Diagram

Block diagram of the proposed system is given below:

Figure : System Block Diagram

As clearly illustrated in the system HLD, wind energy will rotate the wind turbines and by using generator within the wind turbines mechanical energy is converted to electrical energy, this electricity generated by the generator is unregulated and full of harmonics, in order to regulate this supply of electricity a regulator is required which in turn can be used to charge the battery.

Report Structure

This report will give an overview of the techniques and methods used to achieve the final product.

2) Literature review: This section of report concentrates on the literature review regarding wind turbines and their use in modern day energy market. In addition to this technical information regarding components used for this project is also given.

3) Method: Method illustrates the detailed experimental procedures and different stages which are completed in order to attain the end product.

4) Results: The results obtained which are related to the performance of the finished product are given in results section.

5) Discussion and Conclusions: Further discussions on the results and the conclusions drawn after the completion of the project is presented in the fifth chapter.

6) Future work: This chapter presents possible ideas that can be implemented on the designed prototype, to achieve different kind of benefits.

7) References: References of information taken from internet. It also contains Bibliography section with details of the books and the texts, articles, magazines and the data sheets used.

8) Appendices: The appendix contains data sheets of the components use in this project.

Literature Review

Literature Review of this project is divided in following main sections:

History and introduction of wind turbines

Modeling of wind energy and generator

History and Introduction of wind turbines

In the beginning, a structure comprising of blades in the form of a fan was known as a windmill which was used to grind grain and pump water using wind energy. This windmill was later on developed to generate electricity and was renamed a wind turbine. [3] On the other hand a wind turbine is a machine which extracts energy from wind to generate electricity by the rotation of propeller like blades that drives a generator through shafts and gears present within it. It is a rotating machine which converts kinetic energy from wind into mechanical energy and this mechanical energy is converted into electricity using a generator. [4]

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Figure 3: Wind Turbine in Hilly Area [3]

History:

A wind turbine is a machine which extracts energy from wind to generate electricity by the rotation of propeller like blades that drives a generator through shafts and gears present within it (Britannica, 2011). It is a rotating machine which converts kinetic energy from wind into mechanical energy and this mechanical energy is converted into electricity using a generator.

Since ancient times, man has harnessed the power of the wind to provide motive power for transportation. Likewise, the technique of grinding grain between stones to produce flour is similarly ancient, and widespread. Where and when these two came together in the first place is unknown, but a likely scenario suggests a Persian origin, from where the knowledge spread back into Northern Europe as a result of the Crusades. [4] Since the Persian mills were quite unlike the early European designs it seems just as likely that the adaptation of wind as a power source was independently discovered in Europe. Of course wind was not the first non-human power source applied to the task of grinding corn as it was preceded by both animal power, and in all probability by water power.

European millwrights became highly skilled craftsmen, developing the technology tremendously and as Europeans set off colonizing the rest of the globe, windmills spread throughout the world. The basics of windmill design include those built by the British, who developed many advanced control mechanisms over the centuries, and the Dutch who used windmills extensively to pump water and for industrial uses, as well as to grind grain. [5]

As steam power developed, the uncertain power of the wind became less and less economic, and we are left today with a tiny fraction of the elegant structures that once extracted power from the wind. These remaining windmills, seen all over the world, are a historic reminder of a past technological age. A number of mills have been restored either visually or in some cases back to full working order. However the promise of widespread power from the wind lives on both in the form of wind turbines producing electricity, and in the form of small scale wind pumps often largely low-tech installations still used extensively in the world of agriculture. [2]

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Figure 4: An old wind farm[4]

Wind Power in Afghanistan:

Wind power has been used for more than 2000 years and the first windmill used for mechanical purposes was built in Afghanistan in the 7th Century. This was a vertical axis windmill with rectangular shaped blades which was six to twelve sails covered in reed matting and was used to grind corn and drawing water.

windmill39

Figure 5: Historical wind mill in Afghanistan [1]

Wind Power in Britain:

Evidence of windmills in England dates from the 12th century, with earlier references to “mills” generally held to be talking about either animal or water powered mills. The 14th and 15th centuries provide evidence of what the early mills looked like with illustrations in diverse media such as memorial brasses, stained glass, and wood carvings, as well as the expected manuscript records. These early illustrations all showed the simple all wooden post mill structure. The first illustration was shown in the late 1270 A.D which was a four bladed mill mounted on a central post. This was known as the post mill and was already a fair technologically advanced setup as compared to the Persian mills. These mills used wooden gears for the motion of the horizontal shaft to vertical movement to turn a grind stone. [4]

Wind Power in Holland:

As early as 1390 the Dutch set out to refine a design known as the tower mill. This was actually a standard post mill affixed to the top of a multi story tower with separate floors devoted to grinding grain, removing chaff, storing grain and living quarters for the wind-smith and his family. Both the post mill as well as the tower mill designs had to be adjusted according to the wind manually. This was done by pushing a large lever at the back of the mill. Also optimizing the windmill energy and power output plus protecting the mill from damage by furling the rotor sails during storms was the main job of the wind-smith. [1]

Improvement in the design of the Wind mill:

A primary improvement in the design of the European mills was the use of sails that generated aerodynamic lift. This feature improved the rotor efficiency as compared to the Persian mills by allowing an increase in rotor speed and hence which resulted in superior grinding and pumping action.[5]

The process of perfecting the windmill as well as making incremental improvements towards its efficiency took 500 years. By the time the process was completed the windmill sails had major features which were recognised by modern designers as being crucial to the performance of modern wind turbine blades. Some models also featured aerodynamic brakes, spoilers, and flaps.

windmill

Figure 6: Mid 20th Century Windmill [4]

While continuing well into the 19th century the use of large tower mills declined with the increased use of steam engines. The next step in the development of wind power occurred many thousands of miles to the west. [1]

Wind Power in the USA:

For hundreds of years the most important application of windmills at the subsistence level has been mechanical water pumping. This was done using relatively small systems with rotor diameters of one to several meters. These systems were perfected in the United States during the19th century. It initiated with the introduction of Halladay windmill in 1854, and continuing to the Aermotor and Dempster designs. [4]

The most significant modification of the American fan shaped windmill was the development of steel blades in 1870. These could be made lighter and worked into more efficient shapes. But, they worked so well that their high speed required a reduction in gear to turn the standard reciprocal pumps at the required speed. [1] In the late 19th century, advancement was made to the original design and a new type of wind mill known as the multi-blade windmill was manufactured. This design was used in the first large windmill in order to generate electricity.

Wind Power in Denmark:

Poul la Cour was the pioneer of electricity generating wind turbines and he published a journal based on wind power during the same year. Also it was reported that by 1918 around 120 local utilities in Denmark had a wind turbine. The approximated size was from 20 to 35 kW. At that time the wind turbines covered 3 percent of Danish electricity consumption and Danish interest in wind power increased at a high rate. [4]

During the World War, the Danish engineers built a number of two as well as three bladed wind turbines although their concept is a three bladed machine. This type of turbines was used in areas usually based on a wind-diesel setup which ran the electricity supply system. The systems used designs focused on DC (direct current) generators to satisfy their needs but in 1951 these DC generators were replaced with AC (alternating current) generators and therefore became the second wind turbine to generate AC. [5]

In 1980, Christian Riisager, built a small 22 kW wind turbine in his back yard using an earlier design known as the Gedser Wind Turbine (three bladed wind turbine). His turbine design became a success within households around Denmark and this success gave the present day Danish wind turbine designers an inspiration. [3] This inspiration led them to design all their wind turbines and this trend started from 1980 to the present day. A new generation of wind turbines was developed in 1981 and that became a technological breakthrough for modern wind turbines throughout the world.

The serial manufacturing of wind turbines started and Danish manufacturers had much more of a track record than companies and their individual countries. Another thing to note is that California, which is one of the biggest wind farms in the world, has about half of the wind turbines of Danish origin.

20th Century Developments and Modern Wind Turbines:

In the past, the Dutch refined the windmill and adapted it for draining lakes and marshes and when settlers took this technology to the New World in the late 19th century, they began using windmills to pump water for farms and ranches, and later, to generate electricity for homes and industry. [5]20th century was the time when windmills were actually recognised as Wind Turbines. Across the plains they were used to pump water as well as to generate electricity but at the same time as new methods of utilising wind energy were being introduced this trend gradually spread around the world.

windmill

Figure 7: Evolution of Windmill Design in 20th Century

At present the modern wind turbines are based on three blades using AC generators and output is rated in mega watts (MW) or giga watts (GW). Some modern wind turbines are based on four to five blades and they are being used on both AC and DC. The governing body is the World Wind Energy Association and as per their annual World Energy Report, a total number of 76 countries in the world are using wind energy for commercial purposes. The main countries that widely use wind turbines at present include USA, UK, France, Germany, Australia, Denmark, Spain and China. The countries that recently became users of wind energy resources are India, Pakistan and Turkey. These figures suggest an increase in use of high output wind turbines but currently mini or small wind turbines are available and are being used where they have an output power requirement ranging from a few watts (W) to kilo watts (kW). [3]

For a long time individual wind turbines were installed to support single households but now this idea has been advanced to improve the usage of this energy. Nowadays, wind turbines are installed on a large area may that be land or sea. The output is connected to a grid system. Many countries have installed a number of wind farms across their plains and suitable windy locations but the largest on-land wind farm is known as Roscoe Wind Farm and is located in Texas, USA. This wind farm comprises of 627 wind turbines and a total installed capacity of 781.5 MW and provides enough power for more than 250,000 average Texan homes. It is located about 200 miles west of Fort Worth, and covers nearly 100,000 acres. The second largest wind farm is also located in Texas, USA. This wind farm is known as the Horse Hallow Wind Energy Centre and has 421 wind turbines that generate a total capacity of 735 MW. Out of the total 421, 291 of them are 1.5 MW wind turbines and 130 are 2.3 MW wind turbines. The turbines are owned by Florida Power & Light and the company operates 46 other wind farms throughout the US. [4]

1-rosco-wind-farm

Figure 8: Wind farm in England [5]

The largest Off-shore wind farm in the world is the Thanet wind farm. It is located in the North Sea about 7 miles off the coast of Kent, England. The wind farm has 100 turbines and has the capability produce enough energy a year to power more than 200,000 homes. The second largest offshore wind farm is called Horns Rev 2 and is located on Horns Reef in a shallow area off the westernmost point of Denmark. Horns Rev 2 consist of 91, Siemens wind turbines with a total generating capacity of 209 MW. [7]

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Figure 9: Off shore wind farm along the coast of Kent (England) [5]

Future of Wind Turbines:

It is predicted that wind energy will be the most cost effective source of electrical power in the near future. A good part of this prediction has been proven during the current energy rush so its reliability can easily be visualised for future. Recent improvements in wind turbines have shown that the trends which have led to the dramatic fall in the cost of wind energy are set to continue. Countries all over the world are setting their targets for wind power and it is estimated that about 22,000 MW, in the form of 40,000 wind turbines will be installed in the next 10 years. Europe is the hub of this global business and will continue to be as around six companies supply over half of the world’s wind turbines. [6]

As more and more countries start using this reliable source of electricity, master plans are being set for the future. Already the USA, China, Germany and UK have set targets to build further wind farms and each one bigger than the other. As USA has currently the biggest on-land wind farms in the world, they would like to maintain that in the future. Around six wind farms are planned within the USA for the next 15 years and they should be able to maintain the record of largest wind farms in the world. One of the planned wind farms is the Alta Wind Energy Centre in the Mojave Desert California. This farm will have more than 600 wind turbines and when it is completed this will have the capacity to generate 1,550 MW of energy which is double the capacity of the largest existing wind energy farm. USA has no off-shore wind farm but their future plans include the installation and usage of this setup. [6]

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Figure 10: Wind farm in China [6]

China also plans to increase their usage of wind energy and they are also involved in future projects as well as developing wind farms. One of their future aspirations is the under construction Gansu Wind Farm. It has been estimated that when

completed by 2020 and would have the output capacity of 10 Giga watt (GW). They also plan to reach 100 GW overall wind energy output by 2020 as other future wind farms are under construction. By that time it could be the largest capacity wind farm in the world.

In the UK, wind energy is being used extensively and more plans have been set in place for the future. They have more plans to build off-shore wind farms instead of on-land ones as well as to increase the capacity of current setup. Another master plan is to build a wind turbine factory, run by the German giant company Siemens and is expected to complete by 2015.

Germany is also involved in certain future projects as their current setup is highly dependable on wind farms. Currently around 20,301 on-land wind turbines are located in the German federal areas and the country has plans to build more wind turbine farms and reach a high capacity by 2020.They are planning more offshore wind energy as well and predict a capacity of about 10.000 MW by 2020. Most of these off-shore farms will be erected up to 20-60 km away from the coastline.

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Figure 11: Modern wind farm in Germany [2]

Types of Wind Turbines:

Since the development of the wind turbines, numerous designs have been introduced and used worldwide. The difference in these designs was on the basis of size, output power and shape of the wind turbine. The largest wind turbine and the one with the most individual output power up to date is the Enercon-126. Its rated output is about 7 MW and its rotor diameter is 126 meters.

Wind turbines can be divided into two basic types and this is determined by the way the turbine spins. One is the horizontal axis wind turbine and is most commonly used (FIG- 12) while the other one is the vertical axis wind turbines (FIG-13). [3]http://www.ecotownforleicestershire.coop/assets/images/masterplanImages/energyreportVertical-axis-wind-turbine.jpghttp://www.aboutgenerator.com/wp-content/uploads/2010/07/how-to-build-a-wind-turbine.jpg

FIG – 12 [9] FIG – 13 [9]

Horizontal axis wind turbine (HAWT) is the common style wind turbine which has a design similar to that of a wind mill and has blades that look like a propeller that spin on the horizontal axis. The main rotor shaft and electrical generator are at the top of the tower and are pointed into the wind. Small turbines are pointed by a simple wind vane placed square with the rotor (blades), while large turbines generally use a wind sensor coupled with a servo motor. [9]

Since a tower produces turbulence behind it hence the turbine is usually pointed upwind of the tower. Wind turbine blades are made stiff to prevent the blades from being pushed into the tower by high winds. Since the turbulence leads to fatigue failures so most HAWTs are upwind machines. Since the blades always move perpendicularly to the wind they help receive power through the whole rotation. [9]

Small wind turbines are being used extensively in off-grid systems like street lighting, phone booths, lighting up parking areas and public mobile chargers. These wind turbines are usually used with another device such as solar panels and are part of a setup. They are light, easy to install and reliable in all wind conditions.

Green-Column2

Figure 14: Green Column [1]

Vertical axis wind turbine (VAWT) is when the main rotor shaft is arranged vertically. The main advantage of this arrangement is that the wind turbine does not need to be pointed into the wind and can be most reliable on sites where the wind direction is highly variable or turbulent.

In a VAWT the generator and other main components can be placed near the ground so the tower does not need to support it. It is difficult to mount these type of turbines on towers so they are often installed nearer to the base on which they rest, such as the ground or a building rooftop. The wind speed is slower at a lower altitude which means less wind energy is available so air flow near the ground and other objects can create turbulent flow resulting in issues like vibration. However, when a turbine is mounted on a rooftop, the building will generally redirect the wind over the roof and this doubles the wind speed at the turbine. [9]

There are two subtypes of VAWT:

Darrieus wind turbines are commonly called “Eggbeater” turbines as they look like an eggbeater. They are highly efficient but produce large ripple and cyclic stress on the tower which will contribute towards low reliability. They generally require some external power source to start turning because the starting torque is very low. The torque ripple is reduced by using three or more blades which will result in a higher solidity for the turbine rotor. Solidity is measured by blade area over the rotor area and newer models of this type of turbines are not held up by guy-wires but have an external superstructure connected to the top.

Savonius wind turbines is a drag type turbine and are commonly used in cases of high reliability in things such as ventilation systems. Because they are a drag type turbine they are less efficient than a common HAWT but they are excellent in areas of turbulent wind and self starting.

Wind turbine manufacturers:

As wind energy has become a widely used concept, a number of companies have introduced their designs and perfected them. The most popular companies around today are Enercon (Germany), Vestas (Denmark), GE Wind Energy (USA), Siemens Wind Power (Germany), RE Power (Germany), Sinovel (China), Goldwind (China) and Gamesa (Spain).

All these companies are famous for manufacturing as per their own HAWT designs and their systems are being used worldwide. Enercon, Germany based company, is the only company to have made the most powerful and largest wind turbine in the world known as Enercon-126. They continue to work on more ideas and increase the output capability of their wind turbine. On the other hand Vestas which is a Denmark based company is the biggest manufacturer of wind turbines in the world. Most of their wind turbines and installed in Europe as well as USA and their orders keep on increasing day by day as per demand and dependence on wind energy. It was stated that most of the designs from other companies are actually modifications to the original design created by Vestas and this influence can be seen in their systems. [10]

Other companies like GE Wind Energy and Siemens have made major contributions in the manufacturing and enhancing the capabilities of wind turbines of the present age and they are looking forward to the future for more opportunities to make themselves well known within the industry. [10]

Small sized wind turbines made their way into the industry due to the need for smaller and off-grid systems. Marlec Renewable Power is one of the companies that initiated this type of wind turbines and they came up with the idea named Rutland wind turbines. Rutland wind turbines are being commonly used in UK and Europe these days but further international use has been planned due to the interest shown by foreign investors. Rutland wind turbines have current designs using 3 to 6 blades but they are mini versions of HAWT and no VAWT designs have been introduced up to date. They have mostly been used in off-grid systems and add a good combination to the environment surrounded by wind turbines. [10]

Disadvantages of wind turbines:

The strength of the wind is not constant and it varies from zero to storm force. Which means that wind turbines will not generate the same amount of electricity all the time as well as there will be times when they generate no electricity at all.

Many people feel that the countryside should be left untouched so the landscape could be left in its natural form.

Wind turbines are noisy as each one can generate the same level of noise as a family car at very high speed.

People see large wind turbines as unattractive structures and not pleasant to look at. They could disfigure the countryside and might seem a horrible sight.

Wind turbine construction can be very expensive and costly to the surrounding wildlife during the building and installation process.

In some areas of wind farm developments birds have been found dead around the base of turbines.

Many people think wind turbines are a great idea, yet a large proportion of these people would oppose a wind farm development close to their home due to their land price reduction as well as noise pollution.

Modeling of wind energy and generator

In order to develop the prototype circuit in the laboratory, wind energy has to be simulated along with the generator. At first it was decided to use a 12 volt manual generator which can be operated by hand to output 12v so that this can be fed for the rest of the circuitry. A cheap 12v Generator could not be found, very expensive models were available but it was decided not to buy them as it will increase the cost of the product dramatically. Finally, it was agreed that the 12v DC from the power supply will be used to simulate the output of the wind generator.

Method

Method section of this report throws light on the wind power battery charger circuit used and also explains different techniques used in order to build the prototype.

Method section of this report can be sub divided in the following main categories:

1: Research regarding components used in this project

2: Circuit Design and Explanation

3: Circuit Construction

Research regarding components used in this project

At first it was decided to develop a battery management circuit from scratch by using analogue circuitry, buck converter and 555 timer or microcontroller in order to switch the buck converter, but after some research and investigation it was found that there are some specialized ICs available which can be used for managing battery charging circuits.

Different verities of battery management IC were available from Liner technologies, Analogue devices, microchip and National Instruments: but selection criteria for the IC involved: a DIP package for easy prototyping, operating temperature range of -40 to +85â„ƒ, supply voltage rating of up to 18v and cheap in price.

After some search through different vendor websites, LTC1042 seemed to be a suitable candidate for this particular application. After mutual consent it was decided to use LTC1042 as main charge management IC in this project.

Circuit Design and Explanation

Looking through the LTC1042 datasheet, it was discovered that this IC can be adopted for the needs of renewable energy resources and can easily manage different load types based on the amount of energy being produced at one particular time.

Application notes of LTC1042 suggested a circuit for using this IC for managing wind powered battery charger. In order to prove the concept of the system, it is decided to build this circuit and experiment with it.

Chosen Circuit:

The circuit to be built is shown in the diagram below:

Figure 15: Wind Powered Battery Charger Circuit

Circuit Explanation

This circuit behaves in a latching manner, i.e. depending upon the voltage being generated by the wind generator different type of load will be on and off. LTC1042 is a CMOS window and manages the turning on and turning off of different loads.

This circuit contains two batteries and one load, its operation is summarized in the following lines:

1: If the generator output voltage is below 13.8v, charge regulator circuit is active and Ni-Cad battery will be charged through the LM334 current source. If the voltage keeps below 13.8v Lead acid battery will not be charged.

2: If the wind generator output voltage exceeds 13.8v but is maintained below 15.1v, Lead acid battery is being charged through the field effect transistor, Ni-Cad battery will not be charged.

3: If the generator voltage exceeds 15.1v, which can be due to high wind speed, then a fixed load connected to the circuit, which limits generator rpm to prevent damage to it. This load is also switched on using FET after comparing voltages using LTC1042 Window comparator.

Explanation of Window Voltage:

Voltage from the range of 13.8v to 15.1v is chosen to be the window voltage, this voltage is chosen to ensure that the 12v lead acid battery is charged and is prevented to fall in over charging state. By using this window voltage range, it is ensured that the 12v lead acid battery is being charged at the rate of 1Amp/Hour.

LTC1042

LTC1042 is a monolithic CMOS window comparator. Two high impedance voltage inputs, Centre and Width/2, are used to define the middle and width of the comparison window. Whenever the input voltage, Vin, is inside the window the WITHIN WINDOW output is high. The above WINDOW output is high whenever VIN is above the window. By interchanging VIN and Centre, the above Window output becomes BELOW WINDOW and is high if VIN is below the window. Sampling techniques provide high impedance voltage inputs that can common mode to both Supply rails (V+ and GND). An important feature of the inputs is their non-interaction.

Figure 16: LTC 1042

LTC1042 is effectively chopper stabilized, giving it extremely high accuracy over all conditions of temperature, power supply and input voltage range. Sampling technique used to design the LTC1042 is extremely low power consumption. When the device is strobed, it internally turns n the power to the comparators, samples the inputs, stores the outputs in CMOS latches and then turns off power to the comparators, samples the inputs, stores the outputs in CMOS latches and then turns off power to the comparator. This all happens in about 80us. Average power consumption of the device can be made small by lowering the strobe rate. In addition to this an external RC network can be used to strobe the device.

LM334

LM334 is a true floating, three terminal adjustable current source featuring 10,000:1 range in the operating current, excellent current regulation and a wide dynamic voltage range of 1v to 40v. Current is established with one external resistor.

Figure 17: LM334

Initial current accuracy of the device is approximately ±3%. The sense voltage required to establish the current is only 64mv at 25 and is directly proportional to absolute temperature. The simplest one external resistor connection, then generates a current with +033%/ temperature dependence. Zero drift operations can be obtained by adding one extra resistor and a diode.

In this project, LM334 is simply used as a two terminal current source as shown in the figure below.

Figure 18: Circuit Design of LM334

By choosing the as 68 ohm, 1mA current can is generated as shown in the following chart.

Figure 19: Graph of Voltage vs Current(LM334)

Circuit Construction

After going through the details of circuit diagram, it is decided to construct the circuit on the breadboard. For this purpose: 12v Lead acid battery and combination of two 2v NiCad batteries in series are used for charging purposes. 12v battery will be charged if voltage input to the LTC1042 is between the window i.e. 13.8v and 15.1v, on the other hand 4v NiCad battery will be used if the input voltage to the IC is below window, i.e. below 13.8v. In addition to this, one 7W 36 ohm load is sued in order to avoid damage to the circuitry if the output voltage of the generator is above 15.1v, in this case, load is simply dissipating power and protecting the circuit.

A potential divider made of two resistors is used to sense the input voltage which is fed to the pin3 (Vin) of the IC, this potential divider arrangement insures that the input voltage to the input pin never exceeds the maximum absolute rated voltage of 18v. A 1.2 v reference voltage in combination with a 100k resistor is being used to manage the centre point range of the window, where as combination of 215k and 10k resistor is used to reference the width/2 voltage of the LTC1042.

Transistor MTP8N05 are used to either trigger the charging of 12v Lead acid battery or turning on the load of 36ohm. Circuit is build and tested, results of which are presented in the next section.

Results

Testing of any prototype circuit plays an important part to determine product reliability, fault finding and future improvements in the design.

After completely building the circuit, various tests are performed on the circuit, details of which are given in this section. Because, wind generator is not being used in this circuit, generator output is simulated using the30v DC supply.

Test 1 (Current measurement)

In order to charge the 4.5v Ni-Cad battery, a current source of 1mA is used. When the circuit is build, and supply voltage of less than 13.8v is supplied to the circuit, it is found that the amount of current produced is precisely 1mA.

Following table shows the current obtained with various supply voltages:

Supply Voltage (v)

Current (mA)

5

0.99

7

1.1

8

1

9

1

10

0.98

13

0.99

14

1

15

1

Table 1: Supply Voltage vs Current from current source

Test 2 (NiCad Battery Charging)

After the current source was working, it was time to test the charging of NiCad battery. By keeping the input voltage below 13.8v, and connecting an ammeter in place of the battery, 1mA current was measured which suggested that uncharged Ni-Cad battery can be charged using this current, but when the input voltage was increased above 13.8v, no current was measured using the ammeter as now, LTC1042 has input voltage which is within the window, i.e. 13.8v to 15.1v.

Test 3 (12v lead acid Battery)

An uncharged 12v lead acid battery was connected to the Drain of the MOSFET which is connected to the “within the window” output pin of the LTC1042. When the supply voltage from the power supply, simulating wind energy, was changed between 13.8v to 15.1v it was noticed that the lead acid battery stared to get charge, and Ni-Cad batter did not had supply of current which was tested using the ammeter.

Test 4 (Higher Supply voltage)

A 36 ohm 5w resistor is connected to the Above Window output pin of the LTC1042 through the MOSFET, this load is there to ensure that when the voltage generated by the 12v generator is higher than the 15.1v, everything else is turned off where as all the power now is dissipated through this 5w load.

Power dissipation through this resistor is noticed when the supply voltage is increased from 15.1 to 17v. Voltage above 18v is not in the safe test range as it can damage the LTC1042 IC permanently.

After successfully testing the circuit, all the results are discussed in the discussion section.

Discussion

Discussion regarding the overall project and all the results obtained in this project are analyzed in this section of the report.

Detailed analysis, thorough research and investigation regarding the history, present and future of wind mills is presented in this report. At first, research is carried out in order to know the technical details and issues regarding using windmills for the generation of power. It is found that the wind energy and solar energy are two of the major candidates for meeting the future energy demands and highly budgeted research projects are underway to ensure that the proper and reliable technology is developed to efficiently use these renewable energy resources.

Further to the literature review and technical analysis of the windmills, prototype circuit is build by using LTC1042 IC which is a window comparator and compares the input voltage against the centre and width/2 reference voltages.

Two batteries: 12v and 4.5v are charged depending upon the amount of voltage being produced by the wind generator. Wind generator is simulated using the 30v power supply, and supply voltage in the range of 5 v to 17v is simulated using the power supply. Wind powered battery charger circuit operates on the basis of comparing the input voltage with the referenced voltages and then turning the relevant loads on and off based on the voltage being produced by the wind generator.

Results yielded by performing different tests on the circuit are very satisfactory, circuit seems to behave as expected and responds to the change in the supply voltage accordingly by charging appropriate battery and turning on load.

Conclusion

The aim of this project was to design, simulate, construct and test a battery charger fed from a wind energy source. This aim has been successfully achieved after researching, investigating and analyzing the windmills and their use in the power generation systems. It can be confidently said that the wind energy will be a major contributor to the electrical energy in the future. As a lot of research is being carried on around the world for using the windmill based power systems efficiently, this project played its part by developing a system which utilizes renewable energy resources in an efficient way by charging two different batteries based on the amount of energy being produced and also protects the circuit from any damage in case of over voltage.

In addition to this, this project has been a great learning experience and has helped me a lot in developing my research, analysis and circuit building skills.

Future Work

The prototype development of this circuit can lead to the future development of more enhanced and compact size circuitry. Following recommendations are made to improve on this circuit:

As this circuit utilized power supply as its source of energy instead of windmill, future development and analysis on this circuit can be made by using the 12v wind generator and ensuring that the results of this experiment corresponds with the circuit based on 12v wind generator.

If the voltage of the circuit goes above 15.1v, present circuit dissipates power through the fixed 36 ohm 5w resistor, currently all this energy is being wasted. A future upgrade to this project can utilize a combination of 12v battery in series with 1.5v battery to stop wasting the power and charge these batteries instead.

This circuit can be combined with a solar energy based power circuit in order to create smart grid. This concept of smart grid system is quite new but is much more efficient to manage the scares amount of energy efficiently.

References

[1] A guided Tour of Wind mills

http://guidedtour.windpower.org/en/tour/wres/index.htm, January 2009 [5 January 2011].

[2] World Wind Farms(2008).

http://technorati.com/lifestyle/green/article/worlds-largest-wind-farm-now-operational/, July 2008 [18 August 2010].

[3] World of Windmills (2009). Windmills

http://www.windmillworld.com/windmills/history.htm January 2009, [18 December 2010].

[4] Wind Mill History, The history of Wind Energy through 1875

http://www.telosnet.com/wind/early.html, February 2008 [23 January 2011].